SUNRPC: svcauth_gss: enforce krb5 token minimum length
Summary
| CVE | CVE-2026-89550 |
|---|
| State | PUBLISHED |
|---|
| Assigner | Linux |
|---|
| Source Priority | CVE Program / NVD first with legacy fallback |
|---|
| Published | 2026-09-11 20:19:38 UTC |
|---|
| Updated | 2026-09-11 20:19:38 UTC |
|---|
| Description | In the Linux kernel, the following vulnerability has been resolved:
SUNRPC: svcauth_gss: enforce krb5 token minimum length
svcauth_gss_unwrap_priv() validates only an upper bound on the
wire-supplied opaque length before handing the buffer to
gss_unwrap():
if (len > xdr_stream_remaining(xdr))
goto unwrap_failed;
offset = xdr_stream_pos(xdr);
...
maj_stat = gss_unwrap(ctx, offset, offset + len, buf);
The wire value `len` flows unchanged as the upper bound into the
krb5 unwrap path, so a len in [0, 16] passes this check and is
handed to gss_unwrap(). For a krb5 v2 context that lands in
gss_krb5_unwrap_v2(), which reads the 16-byte RFC 4121 token
header fields at ptr+4 and ptr+6 and then calls rotate_left()
before any integrity check. With a sub-header length the header
reads run past the token, and _rotate_left()'s `shift %= buf->len`
path can divide by zero when buf->len has been driven to zero by
the truncated token. A header-only token (len == 16) is equally
invalid: with a non-zero RRC field and the opaque blob ending at
the XDR buffer boundary, rotate_left() builds a zero-length
subbuffer, reaching the same division.
Reject the token at the server entry point before it reaches the
krb5 unwrap core. A valid sealed RFC 4121 token must contain
the 16-byte header plus at least some encrypted payload.
Fix by adding a minimum-length check immediately after the
existing upper-bound check:
if (len <= GSS_KRB5_TOK_HDR_LEN)
goto unwrap_failed; |
|---|
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|
| CNA |
Linux |
Linux |
affected 7c9fdcfb1b64c47ed618c103b617af3f86e1239c dd6afc6cab8c5d387d1ed2f069562ef7bdadd651 git |
Not specified |
| CNA |
Linux |
Linux |
affected 7c9fdcfb1b64c47ed618c103b617af3f86e1239c de942dd8c2c8358bcad04ce44271954c48924423 git |
Not specified |
| CNA |
Linux |
Linux |
affected 7c9fdcfb1b64c47ed618c103b617af3f86e1239c 2eed1e6a976a44015c3ee78841fe336796e2b21c git |
Not specified |
| CNA |
Linux |
Linux |
affected 7c9fdcfb1b64c47ed618c103b617af3f86e1239c a919c5c88769cf8fb3ec071e6078d830bf512489 git |
Not specified |
| CNA |
Linux |
Linux |
affected 2.6.18 |
Not specified |
| CNA |
Linux |
Linux |
unaffected 2.6.18 semver |
Not specified |
| CNA |
Linux |
Linux |
unaffected 6.12.109 6.12.* semver |
Not specified |
| CNA |
Linux |
Linux |
unaffected 6.18.50 6.18.* semver |
Not specified |
| CNA |
Linux |
Linux |
unaffected 7.2.4 7.2.* semver |
Not specified |
| CNA |
Linux |
Linux |
unaffected 7.3-rc1 * original_commit_for_fix |
Not specified |
References
| Reference | Source | Link | Tags |
|---|
| git.kernel.org/stable/c/de942dd8c2c8358bcad04ce44271954c48924423 |
416baaa9-dc9f-4396-8d5f-8c081fb06d67 |
git.kernel.org |
|
| git.kernel.org/stable/c/dd6afc6cab8c5d387d1ed2f069562ef7bdadd651 |
416baaa9-dc9f-4396-8d5f-8c081fb06d67 |
git.kernel.org |
|
| git.kernel.org/stable/c/a919c5c88769cf8fb3ec071e6078d830bf512489 |
416baaa9-dc9f-4396-8d5f-8c081fb06d67 |
git.kernel.org |
|
| git.kernel.org/stable/c/2eed1e6a976a44015c3ee78841fe336796e2b21c |
416baaa9-dc9f-4396-8d5f-8c081fb06d67 |
git.kernel.org |
|
| CVE Program record |
CVE.ORG |
www.cve.org |
canonical |
| NVD vulnerability detail |
NVD |
nvd.nist.gov |
canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.